The performance of a ship particularly with regard to fuel efficiency has become a major consideration because of the current high fuel costs. While ship navigation systems may yield the ships speed across the earths surface, they do not account for effects of ocean currents. Consequently, such navigation cannot be used to determine the ship's propulsion efficiency.
As a ships hull condition deteriorates due to marine growth, bottom paint failure and other factors, the speed of a ship through the water diminishes for a given propulsion power. Thus more power is required to maintain speed or without more power the time at sea is increased. In either case, more fuel is consumed per voyage. In order to monitor conditions so that correction action may be taken at the most efficient time, a measure of the hull efficiency may be determined by measuring the speed of the ship through the water at a standard propulsion power. However, while a number of techniques for measurement of ships speed through the water have been used over the many years by mariners, such techniques have either lacked sufficient accuracy to evaluate hull efficiency or they have required undesirable instrumentation installations aboard ship.
Consequently, it is an object of this invention to provide a means for accurately determining the speed of a ship relative to the water through which it travels. And, the means employs instrumentation that does not require extensive shipboard installation.
Another object of the invention is to measure the speed of a ship relative to a body of water through which it moves, in a highly accurate manner.